CA1256689A

CA1256689A - Low temperature fired dielectric ceramic composition with flat tc characteristic and method of making

Info

Publication number: CA1256689A
Application number: CA000482036A
Authority: CA
Inventors: Charles E. Hodgkins; Mike S.H. Chu; Daniel C. Rose
Original assignee: Tam Ceramics LLC
Current assignee: Tam Ceramics LLC
Priority date: 1984-05-23
Filing date: 1985-05-22
Publication date: 1989-07-04
Also published as: CN85106434A; US4540676A; ATE34374T1; DE3562767D1; JPH0323502B2; CN1007891B; JPS6136171A; EP0169636B1; KR850008654A; EP0169636A1; BR8502421A; KR910002185B1

Abstract

Abstract:
The invention provides a dielectric ceramic composition suitable for forming ceramic capacitors. The composition consists essentially of from about 91.6 to about 95.5 weight percent barium titanate, from about 0.91 to about 1.49 weight percent niobium pentoxide, from about 0.18 to about 0.31 weight percent cobalt oxide, from about 1.04 to about 1.87 weight percent bismuth trioxide, from about 0.68 to about 1.23 weight percent titanium dioxide, from about 0.67 to about 1.20 weight percent lead oxide, from about 0.26 to about 0.46 weight percent boron oxide, from about 0.82 to about 1.49 weight percent zinc oxide, and from 0 to about 0.11 weight percent manganese dioxide.
The composition has improved temperature characteristics when fired at a temperature not exceeding 1150°C.

Description

6~9 LOW TEMPERATURE FIRED DIELECTRIC CERAMIC
j COMPOSITION ~ITH FLAT TC CHARACTERISTIC
., 1 IBackground of the Invention

2 'The pre~ent lnvention relates to a lo~ temperature

3 ~ired dielectric ceramic compo~ition in whlch the dielectric

4 I'constant does not alter from it~ ba~e value by more than 15

5 l~percent over a wide temperature range. More speci~ical1y,

6 I thi~ invention relates to a dielectric ceramic composition

7 ; with a dielectric conQtant Or over about 2400 which is formed

8 I by firing a ba~e ceramic preparation compri~ing a mlxture of

9 l,dlelectric oxide~ and a ceramic flux at temperatures not Ijexceeding about 1150C.
11 1 Multilayer ceramic capacitors are commonly made by 12 !, ca~ting or otherwise rorming insulating layer~ of dielectric 13 ceramic powder, placing thereupon conducting metal electrode ~ layer~, usually $n the form Or a metallic paste, qtacking the I resulting element~ to ~orm the multllayer capacitor, and 16 1 firing to densi~y the material and form a ~olid solutlon o~ !
17 ¦~the constituent dielectrlc oxides. Barlum titanate is one of 18 I the dielectric oxides frequently used in the ~ormation Or the 19 ' in~ulatlng ceramic layer. Because of the high Curie tempera- ¦
20 1I ture o~ barium titanate, however, other oxides are commonly 21 li reacted ~ith the barium titanate to form a ~olid solution, 22 I thereby reducing the Curie temperature of the resulting 23 1¦ ceramic ~aterlal. Becau3e the dielectric con~tant i~ highest 2~ ¦~ at the Curie temperature o~ a materiall it is deqirable that 25 ¦¦ a material for use as a capacitor has a Curie temperature 26 l, around room temperature. Certain other oxides~ such as man- ¦
27 ~ Banese dloxide may also be added to improYe the lnqulation 28 ¦I re~istance and control the dielectric con~tant Or the recult-29 I ing material by acting a~ a grain growth controller.

l T~e variation ~ith temperature of the dielectrlc ~25i~;6~39 1 con3tant of a ceramic composition for u~e in a multi-layer 2 I capacltor i~ al o of qub~tantial ~mportance. Many dielectric 3 ~ ceramic compo~itionQ, ~ncluding barium titanate, have dielec-~ lltric con~tan~ which vary ~ub~tantially a~ the temperature l'increa3es or decrea~e~. In a desirable dielectric ceramlc 6 ~lcomposition ~or a multilayer capacitor used for application~
7 ! requiring stability in the dielectric constant over a wide 8 I temperature range, the dielectric constant does not alter g from it~ ba~e value at 25C (room temperature) by more than I plu~ or minus 15 percent. Aq ~ith the ad~ustment Or the 11 I Curle temperature, reaction of the barium titanate with 12 1 ~elected oxide~ i~ nece~ary to achieve thi3 flat temperature 13 I characteristlc.
The materials commonly used to produce ~uch temper-' ature ~table capacitors with dielectric con~tant~ greater 16 1' than 2000, are generally fired to maturity ln air at tempera-17 li tures greater than 1150-. At these temperature~, the metal 18 1 electrode layer must be formed from the leQ3 reactlve, higher 19 fl melting alloy~ of the ~o-called precious metal~, ~uch a~ pal-l; ladium and ~llver, palladium and gold, and other ~imilarly 21 l expen~i~e alloys well known in the art. Thi3 iq nece~ary in 22 !¦ order to prevent either reaction of the electrode with the 23 11 insulating ceramic layer or melting which might recult ln 2~ ¦I di~continuities in the conducting layer. A method of produc-~l lng a ceramlc composition with a dielectric constant of 26 ,I greater than 2000 with a ~uitable temperature characteriqtic, 27 1I which can be fired at temperatures below 1150~C9 would permit 28 1 the u~e of a le~ c09tly electrode material without sacrific-29 1 lng capacitor perrormance. The dielectr~c ceramic compo~
3~ I tion~ prevlously u~ed to make multilayer capacltor3 at _2-~%56 E;~9 1 temperatures below 1150-r had dielectric constants of leqs 2 than 2000, and thus were not quitable rOr mo~t applicatlon~.
3 Summary Or the Invention ~ It i~ an ob~ect Or the present inventlon to produce a ceramic compo~ition with a dielectric con~tant which is 6 qtable over a wide temperature range. It i~ another ob~ect 7 Or thi~ invention to produce a low temperature fired ceramic 8 co~position with a dielectrlc conqtant Or greater than 2400 g which varies little with temperature.
The above ~tated obJect~ and other ob~ects are 11 achieved by the pre~ent invention, which i~ directed to a low 12 temperature fired dielectric ceramic compo~ition formed from 13 two component~, i.e. a maJor component compri~ing a ba~e 4 ceramic preparation, and a minor component comprising a gla~
frit or ceramic flux. More qpeclfically, in forming the ~6 dielectric ceramie compoqition Or the invention, the maJor ~7 component compri~e~ from about 93.5 to about 96.5 percent by 18 ~eight Or the dielectric ceramic compo~itlon while the minor 19 component compr$ es ~rom about 3.5 to about 6.5 percent by ~eiBht Or the compo~ition.
21 The maJor component of the ceramic composition i~ a 22 baqe ceramic preparation of dielectric oxide~ compri~lng 23 barium titanate (BaTiO3), niobium pentoxide, a~d cobalt 2~ oxide, or their constituent oxides or oxide precursorq.
Preferablyg TAM Ceramics TICON HPB, Product No. 52901, high 26 purity barlum titanate l~ u~ed ln the ba~e ceramic 27 preparation. The compo~itional ranges o~ the component~ of 28 the base eeramic preparation, expre~sed aq the oxide~, are 29 barium titanate from about 98.0 to about 99.0 weight percent, 3~ niobium pentoxide rrom about 0.97 to about 1.54 weight * Trade mark ~25~61 ;19 1, 1 ~percent, and cobalt oxide ~rom about 0.19 to about 0.32 2 , weight percent.
3 I The ceramic flux minor component comprises bi~muth ~ lltltanate~ lead titanate (PbTiO3), zinc oxide and boron oxide, 5 11 or their constituent oxides or oxide precur~ors. The biqmuth 6 1l titanate referred to herein is Bi2Ti207 or its conqtituent 7 l~oxide~ or oxide precur~or~ preqent in amount~ to form 8 ' Bi2Ti207. The compositional range~ of the component~ of the 9 I glass frit are bi~muth titanate from about 16 to about 60 weight percent, lead titanate from about 8 to about 52 weight 11 1' percent, zinc oxlde from about 18 to about 35 weight percent, 12 and boron oxide from about 5 to about 11 weight percent.
13 In additlon, manganese dioxide may be added to the 1~ I mixture Or the base ceramic preparation and the ceramic fluxg 1 either a~ the oxide itself or as a precur-qor, ~uch as manga-16 i ne~e carbonate or a qolutlon contalning mangane~e ions. The 17 ¦i compo~itional range for manganese dioxide i~ ~rom about O to 18 !i about 0.114 percent of the combined weight~ of the combined 19 ll base ceramic preparation and ceramic flux, and pre~erably 11 about 0.05 percent.
21 ¦l In the preferred embodiment, the ba~e ceramic 22 1I preparation comprl~e~ from about 93.5 to about 96.5 percent 23 ¦1 and the gla~s rrit compri~e~ ~rom about 3.5 to about 6.5 24 ¦, percent of the total weight of the dlelectric composition, ¦! ~ith a composition comprislng about 95 ~eight percent ba~e 26 ¦I ceramic preparation and about 5 ~eight percent gla~s frit 27 1l being eqpeclally preferred.
28 1 In the preferred embodiment the ~elght natio of 29 bl~muth titanate to lead titanate in the ceramlc flux ls from about 7.33 to one to about 0.33 to one; and the weight ratio _4--!

Il ~Z56~89 ,, .
"

1 of the additive amounts of bi5muth titanate and lead titanate 2 l'to the additiYe amountq of zinc oxide and boron oxide i~ from 3 labout 3.20 to one to about 1.24 to one. The pre~erred amount ~ o~ zinc oxide with reqpect to base ceramic preparation i9 1l ~rom about 1.22 to about 1.6 weight percent 9 and the 6 1 preferred amount of boron oxide with reqpect to ba~e ceramic 7 1, preparation i~ from about 0.38 to about 0.50 weight percent.
8 ~I The preferred ranges for the con~tituent oxide~ of 9 llthe dielectric ceramic compo~ition are barium titanate from ll about 91.fi to about 95.5 we~ght percent~ boron oxide ~rom 11 j~ about 0.26 to about 0.46 ~eight percent, cobalt oxide from 12 1 about 0.18 to about 0.31 weight percent, manganese dioxide 13 1; from about 0 to about 0.11 weight percent, zinc oxide ~rom 1~ ¦, about 0.82 to about 1.49 weight percent, bismuth oxide from !, about 1.04 to about 1.87 weight percent, titanium dioxide 16 I from about 0.68 to a~out 1.23 weight percent, lead oxide from 17 ~, about 0.67 to ab~ut 1.20 weight percent and niobium pentoxide 18 i from about 0.91 to about 1.49 weight percent.
19 1I The preferred ceramic compo~itions o~ th$s ~ lnvention, formed into multilayer capacitor~, have dielectric 21 ¦! con~tantq which are typically above 2400, di~.~ipation ~actors 22 ¦I which are typically around 1.4 percent at l Vrm~ and 23 I dielectric constantq ~hich vary only plu~ or minu~ 15 percent 2~ I ~ith temperature between -55C and 125~C. The capacitorQ may I be rormed by firing at temperature~ preferably between 1100C
26 I and 1150~C.
27 1~ In an especially preferred embodiment, the ceramic 28 1I dielectric compo3ition i~ formed ~rom a mixture of 95.24 29 ¦ ~eight percent o~ a ba~e c~ramic preparation compr1~ing 98.31 1l ~eight percent BaTiO3, 1.40 ~e~ght percent Nb2O5, and 0.2g 1, , ~S6~g. .
;

~ ~eight percent CoO; 4.76 ~elght percent of a ceramic flux 2 ~ comprising 27.98 weight percent Bl2Ti2Q7, 40.02 ~eight 3 percent PbTiO3, 24.4 ~eight percent ZnO, and 7.6 weight.
~ llpercent B203; and manganese dioxlde ln the amount of 0.05 ! percent based upon the combined weight o~ the ba~e ceramic 6 lipreparation and ceramlc flux.
7 I Detalled Descrlption of the Invention I
8 1 As ~et ~orth below, the dlelectrlc ceramic compo~
g I tion of the present invention has ~everal advantages which I re~ult in ~ubstantial co~t savingq without ~acrificing desir-~1 I'able phy~lcal and electrical propertieq.
I i 12 The pre3ent invention provide~ a novel dielectric 13 i ceramic compo~ition with improved te~perature characteristic t~ '1 whlch can be prepared by firing the component oxldes or l, precur~or3 thereo~ at a temperature not exceedlng 1150-C.
16 lll Thi~ composition di~fers ~ub~tantlally from tho~e diqclosed 17 ~, in the prlor art in which de3irable phy~ical propertie~, ~uch 18 1 aq a higher dielectric con~tant, are ~acrificed in order to ~9 ~l obtain material~ ~hlch can be prepared at ~uch lower 20 ll temperature~. Slnce the prior art materialY had dielectric 21 constant~ which were too low to be of practical use in 22 ~, multilayer capacitors, it ha3 previously been nece3qary to 23 i1 u~e mater~alAq which were fired at temperatures above 1150-C.
24 ¦1 At ~uch high temperaturesl the u~e of electrode~ containing a ll high percentage of preclou~ metal~ ~uch a~ palladium or 26 j platinum i~ neceq~ary. The lower firing temperature of the 27 ceramic compos1tion of the invention permit~ the uqe of 28 l~ qilver-palladium electrodeq ~hich have a 70 percent 3il~er 29 ', and only 30 percent palladium content aq the conducting I! layer~ 1D nultilayer capacitators. Thi~ i~ de~irable because ! .

~6- .

~s~8~

1 palladium, a precious metal, is considerably more expensive 2 than ~llver. Thu~l the use of the ceramic composition of 3 Ithi~ invention in multilayer capacitor~ re~ult~ in ~ I con~iderable cost ~aving~.
I A fired ceramic body of the present inYentlon is 6 produced by reacting during the cour~e of firing the consti-7 l'tuent dielectric oxlde~ Or the base ceramic preparation, B i including barium oxide, titanium dioxide, cobalt oxide, and 9 niobium pentoxide, with a very ~mall amount of mangane~e l' dioxide, and a ~mall amount of gla~s rrit which compri~es 11 ll bismuth trioxide, titanium dloxide, lead oxide, zinc oxide 12 and boron oxide. The oxides o~ the base ceramlc preparation 13 ll and the ceramic flux may be lncluded a~ khe titanate or other combined form3. For example, barium oxide and titanium dioxide may be reacted to ~orm barlum tltanate. Similarly, 16 1 bismuth oxide and titanium dloxide may be reacted to ~orm 17 Ij bismuth titanate; Bi2Ti207. The combined oxides may al~o be 18 I formed from any reaction ~hich will produce them, e.g., the 9 ¦! calcinlng o~ an oxide precursor, -Quch a~ a carbonate or ll nitrate, with other conQtituent oxides or their precur~or~. ¦
21 ll AS i~ well known in the art, commercial preparation~ of 2~ ¦! barium titanate, lead tltanate, bi~muth tltanate and the like 23 l come in ~arious grades and the proportions o~ the constitu- I
2~ 1 entq of the ba3e ceramlc preparation and the ceramic ~lux may ~ therefor require ~llght adJu.~tment using kno~n experimental 26 ll method~ in order to achle~e the de~lred propertie~. ¦
27 ll Alternatively, the fired ceramic body of the 28 1I present lnvention is produced by reacting durin~ the course 29 ¦ Or ririnB a ~a~ter mix prepared by calclning cobalt oxide, 30 ¦I nioblum pentoxide, zinc oxide, boric acid, and manganese i i -7- !

~s668g ~ j carbonate, wlth barium titanate, bismuth titanate and lead 2 Illtitanate~
3 In the present invention, the proportions and ~ l'particle sizes of the constltuent oxides o~ the ba~e ceramic l'preparation, are chosen to maximize the de~ired physical and 6 ~l electrical properties. Niobium pentoxide, when added to 7 ! barium titanate, acts to ~hift the sharp dielectric constant 8 I peak ~hich occur~ at the Curie temperature o~ barium titanate 9 I~ 0-C.) down toward room temperature. It is believed that llwith proper ~election of particle diYtribution~ ~or the 11 I constituent oxide~ a non-homogeneous ~olid solution of 12 I niobium pentoxide will occur along the barium titanate grainq and grain boundaries of the fired ceramic, producing a broad ~ range of Curie temperatures. This produce~ the de ired flat litemperature coefficient of capacitance with a suppressed 16 J I dielectric constant. The cobalt oxide of the base ceramic ~7 preparation ~erves as a flux, and also a~ a charge 18 ; compensator for the pentavalent niobium~
19 ¦~ The constituent~ o~ the ceramic flux were chosen 90 ~o l¦ a~ to achleve khe ~ame non-homogeneous ~olution of the 21 i nioblum pentoxide into the barium titanate grains and Brain 22 j boundarie~ as in the base ceramic preparatlon, but at a 23 ¦¦ lowered firing temperature and with sl1ght further 24 ~1 ~uppre~ion o~ the dielectric constant of the base ceramic.
¦ The zinc oxide and boric acid produce~ a low 26 I vi cosity eutectic compound during the firing proce~s. Since 27 ~inc borate al~o ~uppres3es the dlelectric constantq, the 28 1l quantity of the~e two cons~ituents ~hould be kept a~ low as 29 1~ po~ble. The bi3muth titanate and lead titanate ~erve a~
30 1l hlgher viscosity fluxes to increase the vl~cosity of the ~inc ~ I

~L256~

, .
1 borate formed durlng firing. Bismuth titanate and lead 2 ~titanate, due to their much higher dielectric constants and 3 Curie temperatues, mlnimize the suppre~sion of the dielectric ~ Iconstant while serving aQ fluxing agents. In addition, the Iratio of zinc oxide to boric acid and the ratio of bi~muth 6 li titanate to lead titanate were cho~en to help balance the 7 I charge compen~ation and overall stoichiometry of the fired 8 I'ceramic which i9 known to be very important ln the art.
9 , The mangane~e oxide con~tituent, due to its !Imultlple valence levels, is very ef~ective ln balancing out 11 llthe acceptor-donor ions. In this capacity, the mangane~e 12 oxide improveq She inQulation re~istance Or the fired 13 l ceramic.
~ In preparing the base ceramic preparation used in ' the invention, the con~tituent oxides in the proportions set 16 1'l forth above may be slurrled together in water. After drying, 17 I the ~ixture may be blended with the ceramic flux composition 18 l; and the mangane~e dioxide. The ceramic flux composition may 19 ¦I compri~e a mixture of the component oxides, or the flux I component oxldes ~ay be melted together, quenched 9 and 21 !I pul~erized into a single component ~rit. The combined 22 ! mi%ture Or the base ceramlc preparation, the ceramic flux 23 I composition and the manganese dioxide may be cast lnto a 2~ ll sheet using ~tandard methods, formed into a multilayer il capacitor ~tructure with, e.g., 70 percent silver-30 percent 26 l' palladium electrodes, and rired at about 1110~C to 1150~C for 27 1 about 3 hour~O
28 i ~he low temperature-fired dielectric compo~ition of 29 ~ this lnvention has an lnsulation re~i-qtance-capacitance i product (RC) greater than 10,000 ohm-farads at 25-C and 50 ll _9_ I1 ~2S66~3~

1 VDC/mil and greater than 2000 ohm-farad3 at 125C and 50 2 VDC/mil. The dielectric conqtant ici typically about 2500 3 ! ~ 200 at 1 KHz and 1 volt rms, and the diqqlpation ~actor i~ j ~ typically about 1.8 ~ 0.2 percent at 1 KHz and 1 volt rms.
5 1l Dielectric breakdown voltage rangeq from about 650 VDC/mil to 6 about 950 VDC/mil.
7 ll Of particular lmportance i~ the ~act that the 8 Il dielectric con3tant of the ceramlc compo~ltion of the inven-9 lltion varles little and predictably with temperature. In a ~; deqirable dielectric ceramic composition for uqe in multilay-11 i' er capacitor~ ~here temperature 3tability i~ of importance, 12 the temperature coefficient of capacitance is such that the 13 1 dielectric constant does not alter from its ba~e value at 14 1 25-C by increaqing or decrea~ing more than 15 percent in the 1 temperature range between minus 55-C and 125C. This value 16 also repre~ent~ a specification ln the ceramic indu~try known 17 ! aq the X7R temperature characteriqtic- In the dielectric 18 ll ceramic compo~ition of the present invention, the temperature 19 1~ coefficient of capacitance ~eet~ thi~ 3tandard.
20 ll The invention ~ill be further illuitrated by the 21 1~l following exa~ple~, but the invention iq not intended to be 22 limited theret~. The ~alues given for the exampleq herein 23 1l are ~ub~ect to variations based on factors known in the art.
2~ ¦I For example, with respect to Exampleq 1-31 herein, the ll dlelectrlc constant ~ay be ~ignificantly increased and the 26 I dissipation ~actor may be ~ignificantly decreased by 27 I pulverizing, milling, uniformly di~persing, or otherwi~e 28 ll reducing the ~tarting ~aterials to very fine particles. Such 29 l' practices, ~hich are oo~monly carried out in the course o~
1 ~anufacturlnR ceramic capacitor~, were not employed to their i ~L25~6~3~

1 I full extent in the preparatlon o~ Exampleq 1-31. In addition, 2 ~lvariation~ in ~irlng sonditionq, ~ample thickne~ and 3 , preparation, and mea~urement error may re~ult in dlfferences ~ ¦lin the observed ~alue~ for the ~ame compo~ition. Thus, 5 ~ll depend~ng upon manufacturing techniques, and without regard 6 1~to particle Qize, the properties of ceramic compo~ltion made 7 ll using the proportion~ given in Example~ 1-31, can vary from 8 values glven; ~or example the dielectric con~tant~ may vary 9 I by 1 200, the di~qipation factor may vary by ~ 0.2 percent, ;l and the capacitance change with temperature versuq 11 Ijcapacitance at 25-C ~ay vary by ~ 1.5 percent.
12 ! Exampleq 1-7 ! ~ _ 13 Effect of !i Variation of Ratio of Ceramic 1~ ~i Flux to Ba~e Ceramic Preparation li _ 15 1l A ba~e ceramic preparation ~a~ prepared by 16 il ~lurrying in ~ater 49.15 grams of TAM Ceramic.q TICON HPB high 17 ii purity barium titanate, 0.70 gramq of technical grade ~ine 18 particle size niobiu~ pentoxide, and 0.15 grams o~ technical 19 l¦ grade r~ne particle ~lze cobalt oxide. Firty gramq of the 1 ba~e ceramic preparation wa~ mixed with zero to five gram~ o~ ¦
21 l¦ ceramic flux compri~ing 41.2 weight percent of bi~muth 22 ll titanate (~i2Ti207~, 26.8 weight percent of lead titanate 23 ll (PbTiO3~, 24.4 ~eight percent zirc oxide (ZnO), and 7.6 2~ ¦I weight percent boron oxide ~23 wa~ added in the form o~
¦I boric acid (H3B03). The ratio of flux to base preparation 26 1l for each of Examples 1-7 l~ ~ho~n in Table 1. Fcr each 27 j' ~ample, mangane-~e carbonate ~a~ added to the resultlng mlxed 28 ¦ po~der Or the ba~e ceramic preparation and the ceramic flux 29 j in an a~ount con~titut~ng 0.057 weight percent of the total powder. The ceramic powder mixture ~a~ added to 25 mllli-!
i ~L2566~39 1 liters Or distilled water and mixed thoroughly in a high 2 I speed Spex paint mixer for 10 minutes. The re5,ultant slurry 3 ,, waq then dried into a cake and ground in a mortar and pestle.
Four milliliters of a binder solution including 26 weight I percent water, 26 weight percent propylene glycol, and 48 6 1! weight percent corn syrup was mixed into the ceramic powder 7 1 ln a mortar and pestle and then granulated through a 40 mesh 8 j nylon screen- Diqcs of the resultant mixture having a 9 1I dlameter o~ 1.27 centlmeter-q and a thickness of 0.1 to 0.15 I' centimeters were presqed at a pre~sure of 38,000 lb~. per square lnch in a ~tainless qteel die. The diqcs were placed 12 I'on a stabilized zirconia setter and fired at temperatures 13 I from 1110-C to 1150C ror 3 hours.
1~ l' A~ter cooling, the thickneqs and diameter of the Isintered ceramic discs were measured with a micrometer and a 16 ~Ivernier caliper. Silver electrodes were painted on the ma~or 17 ! surface~ and then ~ired at 850- C. to ~inter on the 18 i electrodes. The capacitance, di-Qsipation factor (DF), and 19 l capacitance change with temperature ver~u~ capacitance at l,25-C (TC) were then meaqured with an Electro Scientiric 21 ~ Induqtries, Inc. model 2110A bridge at 1 KHz 1 Vrm~. At 22 leaqt three discs rrom each example were measured. The 23 l~ea~urement and temperature variatlon~programming were all 2~ Icontrolled by computer and microprooes30r9 and the I,measurement tep~ ~ere carried out according to accepted 26 ! industrial practice.
27 l, The dielectrlc con~tant (K), of each disc wa~
28 il calculated accordlng to She ~ormula:
29 ~ = 5.66 x C25 x R xlol2 1l !

~s6~a~

where C25 i5 the capacitance value at 25~C; Q i5 the thickne~ Or the dl~c in lnches; and D is the dlameter of the disc in lnches.
The result~i are 3hown in Table 1, ~rom which it can be ~een that ~hen the rlux/base ceramic preparatio~ weight ratio i~ le~3 than 0.0357 such a~ in Examples 1 and 2, the dielectric ceramic composition will not be ~intered to qufficient den~ity and TC at minuq 55-C ls greater than 18~.

. , .
~hen the flux/baqe ceramic preparation ~eight ratio i~
greater than 0.065, ~uch a~ in Example 6 and 7, the dielectric constant was reduced to below 2100. The~e compo-I ~itions would be of little practical u~e even though they !~ demonqtrated lmproved di~sipation and flatter TC characteris- I
' tic~.

Table 1 i Effect of Variation of Ratio of ~ramic ~ ~ to ~e Ceramic Preparation , Capacitance C~e ~ith Temperature ll v. Capacitance at 25-C (TC) jI ~ux~e Geramic TC TC TC TC
Wt. ~tio ~ ~F 55DC -30C 85~C 125C

1 0 Will not ~inter l! 2 .02 2230 1.45%-19.8~ -15.3~ -9.4% -6.1 ¦l 3 .035 2380 1.23 -17.2 -13.2 ~3 4 3.8 4 .05 2360 1.15 -15.3 -11.5 -~.t 8.8 .065 2160 1.08 -12.5 -8.6 0.4 10.1 6 ~08 2090 1.06 -11c8 8.2 1.3 12.0 7 .10 2055 1.07 _13.2 -9.4 2.2 13.2 l l l !! ~

i6~3~

1 Examples 8 2 I Yariation of Amount of Manganese 3 Fifty grams of base ceramic preparation powder as ~ de~crlbed in Example~ 1-7 ~as mixed with 2.65 grams Or ~j ceramic flux a~ described in Examples 1-7. Hanganese ~ 1l carbonate wa~ added to the resulting mixed powder in varying 7 ll weight percentage~ as set forth for Examples 8-11 in Table 8 ll 2. Ceramic discs were prepared and ~intered in the same g ,I manner as de~cribed in Examples 1-7. The dielectric ll properties ~ere mea~ured and are set forth in Table 2. The 11 .~ addition of man8ane~e carbonate improved the dis~ipation 12 I factor and the TC of the ceramic dielectric compo~ition.
However, ~hen more than 0.190 weight percent ~anganese carbonate wa~ added, such as in Example 11, the dielectric 15 ll constant was reduced to leq-Q than 2100, resulting in a 16 I, material lmpractical for use ln a multilayer capacitor as 17 l, deQcribed herein, 22 I.

~5 11 //
26 !l //

28 Ij . 14 i, i ~L2~i$689 Table 2 2 Effect of Variation of A~o~t_o~ ane~e 3 Capacit~ce ~ange With Temperature Ii Wt S TC TC TC TC
IlEx~ MnC0 R DF -55C _30C 85JC 125C
, i-- 3 1l8 0% 22401.14% -1S.7% -12.2% -1.4% 7.7 7 j,4 0.057~22501.06 -17.3 -13.5 -3.3 5.6 "
8 ll9 0.114S21900.94 ~ .9 =11.7 0-9 8.2 9 ll10 0.190~21150.82 -14.1 -11.7 -1.0 8.4 1111 0.285~20700.62 -13.0 -11.0 -0.7 9.
I!

Example~ 12 17 1~ ii Variation of Ratio Or Bi.~muth Tltanate to Lead Titanate Fifty Bram~ of ba~e ceramic preparation powder a~
16 !I described ln Example~ 1-7 wa~ mixed with 2.65 gram~ of a 17 ll ceramic rlux. In each example the ceramic ~lux contained 68 18 l weight percent of bi~muth titanate and lead titanate 19 ¦I combined, 24.4 ~eight percent of zinc oxide and 7.6 welght !i percent of boron o~ide. The ~eight ratio of bl muth titanate 21 ll to lead titanate ~a~ varied aq ~et ~orth in Table 3.
22 ¦I Mangane~e oarbonate ~as added to the total base ceramic pre-23 l paration/ceramic flux powder in an amount of 0.057 weight 2~ percent. Ceramic di~c~ were prepared and ~intered, and the dlelectr~c properties mea~ured, a~ ~et forth ln Example~ 17.
26 The re~ult~ are summarized in Table 3. From the3e example~
27 ll it can be ~een that ~hen the bi~muth titanate/lead titanate 28 weight ratio increa~edg the dielectric con~tant of the 29 I d1ielectric ceramlc co~posit1on decrea~ed~ goin~ to 2000 when, , a~ in Example 12, no lead titanate ~a~ included. ~hen the I 1, .l -15- , .

~25668g 1 bl~muth titanate/lead titanate ratio went to zero t such as in 2 I Example 17, the value for TC at -55-C exceeded -15 percent, 3 jj even though the dielectric constant was high and the 4 l diQ~ipat~on ractor wa~ low. The compositions of Examples 16 '¦ and 17, where the bi~muth titanate/lead titanate ~eight ratio 6 l ~aa lower than 0.333 are less deqirable than, for example, 7 ! the composition Or Example 4, lncluded here for comparison 8 , purpo3es, because lead titanate has acceptor ef~ects which 9 j~ lntroduce a ~econd peak in the TC characteristic~ beginning l~ at about 45C and ~hich also cause TC at 125 C to become 11 I much more negative than ceramic composltion~ with a bi~muth 12 ~~ titanate/lead titanate weight ratio greater than 0.333.
13 ,~ Although it is not apparent ~rom examination of 14 ll Table 3, and the capacitance variation ln Example 16 i~ ~till 1 within ~15~ rrom -55 C to 125 C, the compo3ition of Example 16 16, when applied in a multilayer capacitor deslgn, haq a high 17 ll potentlal to develop a ~econd peak at about 45C whlch 18 ! exceeds +20~ due to additlonal acceptor contamination which 19 1¦ is very common ln multllayer capacltor processea.

21 1! // !

23 1~
2b, 1 //

26 , //

~!8 29 l' // i , ,! -16-l, l 1~ ~L25~89 1 1 able 3 2 '~ Variation in Ratio of Bi~m~h Titanate to Lead ~tanate ll Capacitance Change With Temperature 11 Orv. Capacitance at 25~C- (TC?
I ~i Ti 0 i ~O 2 7 TC TC TC TC ¦
6 ,~. PbTiO K DF -55C -30C 85C 125C
7 ll12 ~ 2000 1.11 -14.5 -10.1 2.6 13.6 8 13 7.330 2135 1.36 -15.3 -10.7 1-3 11.5 9 1'4 3.050 2220 1.O9 -16.4 12.2 0.7 11.3 0 il 4 1.540 2250 1.06 -17.3 -13.5 -3.3 5.6 ~ 15 0~700 2300 1.05 -15.5 -12.0 -1.8 7.6 12 I! 16 0-333 2380 0.99 - 14.6 -11.1 -2.8 5.6 3 ll17 o.ooo 2450 0.87 -17.~ -13.9 -5.9 -1.2 No lead titanate wa~ included in the composition Or EKample 12.
'I
16 I Example~ 18-25 17 I Varlation Or Ratio of Bi~muth Titanate plU9 Lead Titanate to ! Zinc Oxide plus Boron Oxide 19 In each Or Example~ 18-25, 50 gram~ of base ceramic I preparation as de~cribed in Examples 1-7, wa~ mixed with 2.65 21 ll gra~s Or a cera~ic ~lux and the re~ultant mixed powder wa~
22 l~ ed uith 0.057 percent by weight of mangane~e carbonate.
23 The ceramic flux compo~ition of the~e example~ was varied 1 ~ith re~pect to the amount of hi~muth tltanate and 1ead 2~ ~ titanate combined ver3uq the amount of zinc oxlde and boron 26 ! oxide comblned. A mixture of 60.4 grams of bi~muth titanate and 39.6 gram~ Or lead titanate was prepared, a4 wa~ a mix-¦I ture Or 78.2 gra~ of zinc oxide and 21.8 grams o~ boron ¦~ oxide. The weight ratio o~ the bi~muth titanate/lead Il titanate ~ixture to the zinc oxide/boron oxide ~ixture ~a~
,,1 Il -17-, ~L25~6~3~

1 varied a~ set forth in Table 4. Ceramic di~cs were prepared 2 I and ~intered, and the dielectric propertie~ mea~ured a~q 3 ' described in Examples 1-7. The reqult3 for each example are ~ -¦ set forth in Table 4. AQ can be seen from the re~ult~, when 5 1I the weight ratio of the bismuth titanate/lead titanate compo-6 ¦I nent to the zinc oxide/boron oxide component wa~ greater than 7 1I 3.2, such as in Example 18, the ceramic dielectric composi_ 8 1I tion cannot be sintered to be ~urficiently den~e. There~ore, 9 1I the dielectrlc constant was low, the dis~ipation ~actor was high and the TC was large for thi~ example. When the ~ame 11 ¦i ratlo waq le~s than 1.24, ~uch as in Examples 22-25, the 12 l, ceramic composition became ~emiconducting and the TC
13 ll characteristics became exceedingly large. Examples 24 and 25 14 l most clearly demonstrate the nece3~ity ~or adding the bismuth titanate and lead titanate component~ in order to achieve the 16 1I flat temperature characterl3tic of the lnvention, 18 jl /
lg 11 ~L%5~

1 ble 4 2 !l Variation Or Ratio of Bismuth ~tanate Plus ~ad ~tanate to Zinc Oxide plus ~oron Oxide ~t. ratio ~ I ( i2~207 Capacit~ce Change ~lth Temperature 5 1 ~ v. Capacitance at 25C. (TC) ll PbTiO3) 6 ll to TC TC TC TC
IIEX.(ZnO ~ B~03~ K DF -55~C-30-C 85C 125C
18 4.88 2210 1.36 -17.413.3 -0.7 11.4 ',19 3.20 2300 1.33 -18.3-14.3 -0.9 8.~
9 1¦ 2.13 23601.15 -15.3-11.5 -1.1 8.8 ll201.37 22201.05 -13.0-9.5 -3.0 5.0 12 ~i211.24 2~701.09 -15~5-11.5 -4.6 1.3 22 1.0~ 23901.32 -18.0-15.2 -2.6 -4.1 I, 230.57 18901.38 -0.7-3.3 71.7 -6.7 1~ 'I
24 0.00 23200.92 _54.1-39-7 14.8 -37.6 l250.001~ 28000.88 -34.9-25.3 _5.1,-28.2 16 1ll 17 !!~ 2% total IExample~ 26-31 ~IYariation of Amount o~ ~inc Oxide and Boron Oxide I,In each Or Examples 26-31, 50 gram~ o~ ba~e ceramic 23 1 preparation po~der a~ de~cribed ln Example~ 1-7 was mixed I with 1.03 Brams of bismuth titanate, 0.67 gram3 of l~ad ~ titanate~ and with the ratio of the weight~ of zinc oxide and 26 ' boron oxide to total powder weight ~aried a ~et ~orth in Il Table 5. Mangane3e carbonate wa added to the total mixture I of each example ln the amount of o.n57 percent by weight. I
2~ I Cera~ic discs were prepared and ~intered 9 and the dielectric I

8~
. .

1 , properties were measured a~ descrlbed in Examples 1 7. The 2 I re.Qult3 are 3et forth in Table 5. A~ can be ~een from Table 3 ' 5, when the boron oxide to total powder ratio is greater than 4 ¦~ .005 such as in Example 27, the dielectric constant wa.Q
5 'll reduced to below 2100, and was too low to be of practical 6 1 use. When the zinc oxide to total powder ratio is greater 7 l~ than .016 ~uch as in Examples 30 and 319 the resulting sample 8 '' became semiconductine and widely varying TC characteri~tics 9 Il were pre~ent. As can be seen from Example 31, a composition containing a zinc oxide to total powder ratio o~ .020 ~howed 11 l' a ~econd peak far above 15% in the TC, and thus compo~it~on~
12 ll with elevated amounts Or zinc oxide are unsuitable for u~e in 13 ' multllayer capacitor~ according to thi~ lnvention.

15 I Table 5 16 IVariation of Amount of Zinc Oxide and 8Oron Oxide 17 ¦, ~ ratio ~t. ratio Capacitance Change With Temperature 18 !1 of of v. Capacitance at 25C. (TC) _ ~I ZnO B O
19 ll to tot~ t~ ~otal TC TC TC TC
1 ~- er po~er K DF55-C -30aC85DC 1?5 C
¦1 4 .0122 .00382250 1.06-15.3-11.5 -1.1 8.8 '26 .0122 .00482210 Or99-12.3- 8~8- 0~8 9~0 22 `27 .0122 .00762000 O.91-9.7 -6.g 0.3 g.5 23 128 .0140 .00382450 1.18-13.9 -9.B -0.7 8.9 1 29 .0160 .00382450 1.21-15.2-11.2~1.9 6.8 l3 .0180 .00382500 1~52-19~8-16~7 1.2 -0.8 26 l31 .0200 .oo381930 1.76-14.1-15.6 73-8 13.7 28 ll , A cera~ic powder slurry wa~ prepared by mlxi~g and 3o ~ -20-~2~ 9 1 diqpersing uniformly 474.6 gram~ of the base ceramic prepara-2 tion powder described in Examples 1-7, 6.6 grams bi~muth 3 titanate, 9.5 ~ram~ lead titanate, 5.8 grams zinc oxlde, 3.2 ~ gram~ boric acid, and 0.3 gram~ manganese carbonate with 5 8rams Or Nuodex v1444 ~urfactant, 20 gram~ Or toluene, 5 6 grams Or ethanol, and 250 grams of binder solution made by 7 unlformly mlxing and dissolving 27.5 grams Or Butvar B-76 8 vinyl re~in, 5 Bram~ Or Nuode~ V1444, 13.8 grams of dioctyl g phthalate, 163 gram~ of toluene and 445.8 grams of ethanol.
The resultant slurry was milled ~or 16 hour~ and di~charged 11 and riltered through 44 micron ~creen. 360 gram3 of the 12 resultlng slip, having a viscosity of 4960 centipoise, was 13 further mixed wlth 4.8 grams of toluene and 1.2 gram~ of 1~ ethanol to ad~u~t its vlscoslty to 3360 centipoi~e. The ~lip wa~ then vacuum de-alred and cast lnto a strlp or tape having 16 a thickne~s of 2.4 mil by procedures commonly known in the 17 art. The tape was converted into multilayer ceramic 18 capacltor~ with 70 percent ~llver-30 percent palladium 19 electrode~ via conventional proces~es well known ln the indu9try. The capacltors ~ere preheated to 260'C for 48 21 hours, placed on ~tabillzed zirconla or high density alumina 22 ~etters and ~intered at lllO-C to 1140~C for 3 hours. The 23 sintered capacitor~ had 10 active d~electrlc layer~ ~ith 24 dielectric thickness of 1.75 mll. Electrode~ Or Dupont sil~er paint No. 4822 were applled at opposlte ends of the 26 multllayer capacltor to connect alternate layer~, and the 27 capacltor wa3 flred at 815-C ln a tunnel furnace. The dlelec-28 tric properties Or the resulting capacltor~ were dlelectric 29 constantr 2600 ~ 200 at 1 RH~ and 1 volt rm~; dis3ipation factor: 1.4 0.2 percent at 1 RH~ and 1 volt rm~; TC: W12.0 * Trade mark -21-~ ~3 ~2~66~g .
1 ~ 1.5 percent at -55-C, -9.0 + 1.5 percent at -30~C, -4.0 2 ~ 1.5 percent at 85-C, snd -0.5 ~ 1.5 percent at 125C; RC:
3 i; greater than 3000 ohm-rarad~ at 25C and 50 VDC per mil and ~ ll greater than 1650 ohm farads at 125-C and 50 VDC/mil for 1l capacitorq rired at 1110-C, and greater than 10,000 ohm-6 1 farads at 25-C, 50 YDC/mil and greater than 2000 ohm farad~
7 1l at 125-C, 50 VDC/mil for capacitorq fired between 1120C and 8 ll 1140C. ~he dlelectric breakdown voltage of the multilayer g I capacitor~ prepared according to this example wa~ greater I than 680 VDC/mil.
~ Example 33 1~ A ceramic ma~ter m~x waq prepared by dry mixing and 13 ! blending a 3.73 kilogram~ grams cobalt oxide, 17.27 kilograms t4 ¦I niobium pentoxide, 15.16 kilograms zinc oxide, ~.45 kilogram~
15 ll boric acid, and 0.747 kllogram~ mangane~e carbonate in a 16 ' large scale cone blender for 2 hours. The powder mixture was 17 1! then calclned at 815 to 825-C for 3 hour ln a tunnel kiln.
18 ! The calcined material wa~ then pulverized and placed in a 19 ¦l ~ibratory energy ~ill with alumina media io deionized water 1 st about a 55 ~ei8ht percent powder eontent. The ~lurry wa3 21 I! milled for 10 1/2 hour~, discharged, dried and pulverized to 22 1 1.4 micron particle ~ze and 4.97 M2tgram ~urface area. A
23 1~ ceramic dielectric compo~ition was prepared by dry mixing and 2~ ¦ blending 424.7 kilogram~ TAM Ceramic~ TICON HP8 h~ gh purity ' barium titanate, 6.05 kilograms bismuth titanate, B.636 26 ll kilogram~ lead tltanate, and 14.22 kilograms master mix, a~
27 described above in a large ~cale cone blender for 2 hourq.
28 I The re~ultin~ powder mi~ture had an average particle ~i~e of 29 ll 1.3 micron~ and a ~urface area of 2.59 M2/gram. 400 grams of 3~ ll the re~ultlng dielectric composition ~a~ charged into a "

~IL2S~689 , 1 pebble mill ~ith 1/2 inch alumina media toeether with 218 2 ~ grams o~ a binder solution made by uniformly mixing and dis-3 1 ~olving 24 gram~ Butvar B-76 vinyl resin, 40.4 gram~ Nuodex ~ ll V1444, 12 grams of dioctyl phthalate, 142 grams of toluene I and 35.5 grams o~ ethanol. The slurry was milled for 16 6 hours and di~charged and filtered throu~h a 44 micron screen.
7 ~, The ~lip, with a vi~co~ity of 1880 centipoi~e, wa~ then de-~ I! aired and caqt in accordance with qtandard techniqueq into a g j tape with a th~ckne~s of 1.5 milq. The tape wa~ converted ~' into multilayer ceramic capacitors with 70 percent qilver-30 11 I percent palladium electrode~ in accordance with techniques 12 qtandard in the induqtry, qintered and provided with silver 13 1 electrode~ a3 de~cribed in Example 31. The ~intered ceramic ' capacltor of thi~ example had 10 active dielectric layers j wlth a dielectric thickne~ Or 1.0 mils. The dielectric pro-16 ll pertie~ o~ the capacltor of this example were dlelectric 17 Ij con~tant: 2600 ~ 200 at 1 KHz, 1 vrmq; dic~ipation factor:
18 ¦ 1.8 ~ 0.2 percent at RHz, 1 vrms. The temperature 19 ll characteristic, TC, waq -8.0 + 1.5 percent at -55-C, -5.5 ¦l 1 1.5 percent at -30-C, -2.0 + 1.5 percent at 85-C, and 3.0 21 1! + 1.5 percent at 125-C. The in~ulation resistance-22 1¦ capacitance product, RC, was greater than 10,000 ohm-farad~
23 ¦1 at 25-C, 50 YDC/mil and greater than 2,000 ohm-faradY at 2~ 1 125-C, 50 Y~C/mil. The capaciSance change with 8 50 VDC bia~
il at 1 RHz, 1 vrmq wa~ 19.0 + 2.0 percent at 25-C, -24.0 ~ 2.0 26 ¦I percent at -55-C and -24.0 1 2.4 percent t 125-C. The 27 1 dielectric breakdown voltage for the multilayer capacitor of 28 ~I this example was greater than 900 YDC per mil.

I

.,

Claims

What is Claimed is:

1. A dielectric ceramic composition consisting essentially of from about 91.6 to about 95.5 weight percent barium titanate, from about 0.91 to about 1.49 weight percent niobium pentoxide, from about 0.18 to about 0.31 weight percent cobalt oxide, from about 1.04 to about 1.87 weight percent bismuth trioxide, from about 0.68 to about 1.23 weight percent titanium dioxide, from about 0.67 to about 1.20 weight percent lead oxide, from about 0.26 to about 0.46 weight percent boron oxide, from about 0.82 to about 1.49 weight percent zinc oxide, and from 0 to about 0.11 weight percent manganese dioxide.

2. A dielectric ceramic composition formed by firing a mixture comprising (a) from about 93.5 to about 96.5 percent by weight of a base ceramic preparation consisting essentially of metal oxides or precursors thereof in proportions to provide, in the oxide form, from about 98.0 to about 99 weight percent barium titanate, from about 0.97 to about 1.54 weight percent niobium pentoxide, and from about 0.19 to about 0.32 weight percent cobalt oxide; (b) from about 3.5 to about 6.5 percent by weight of a ceramic flux consisting essentially of metal oxides or precursors thereof in proportions to provide, in the oxide form, about 16 to about 60 weight percent bismuth titanate (Bi2Ti2O7), about 8 to about 52 weight percent lead titanate, about 18 to about 35 weight percent zinc oxide, and about 5 to about 11 weight percent boron oxide; and (c) manganese dioxide or precursors thereof in proportions to provide manganese dioxide in an amount of from about 0 to about 0.114 percent of the combined weight of said base ceramic preparation and said ceramic flux.

3. A dielectric ceramic composition in accordance with Claim 2 wherein said mixture comprises about 95 weight percent of said base ceramic preparation and about 5 weight percent of said ceramic flux.

4. A dielectric ceramic composition in accordance with Claim 2 wherein the ratio of the weight of said bismuth titanate to the weight of said lead titanate is between about 7.33:1 and about 0.33:1.

5. A dielectric ceramic composition in accordance with Claim 2 wherein the ratio of the combined weight of said bismuth titanate and said lead titanate to the combined weight of said zinc oxide and said boron oxide is between 3.20:1 and 1.24:1.

6. A dielectric ceramic composition in accordance with Claim 2 wherein said zinc oxide is from about 1.22 to about 1.60 percent of the combined weight of said base ceramic preparation and said ceramic flux.

7. A dielectric ceramic composition in accordance with Claim 2 wherein said boron oxide is from about 0.38 to about 0.50 percent of the combined weight of said base ceramic preparation and said ceramic flux.

8. A dielectric ceramic composition in accordance with Claim 2 wherein the dielectric constant is greater than 2400.

9. A dielectric ceramic composition in accordance with Claim 2 wherein said composition is formed by sintering said base ceramic preparation, said ceramic flux and said manganese dioxide or oxide precursors thereof at a temperature between about 1100°C and 1140°C.

10. A dielectric ceramic composition in accordance with Claim 2 wherein the capacitance of said composition varies with temperature from the capacitance at 25°C about 15 percent or less at temperatures between about -55°C and about 125°C.

11. A dielectric ceramic composition having a dielectric constant greater than 2400, said composition consisting essentially of from about 91.6 to about 95.5 weight percent barium titanate, from about 0.91 to about 1.49 weight percent niobium pentoxide, from about 0.18 to about 0.31 weight percent cobalt oxide, from about 1.04 to about 1.87 weight percent bismuth trioxide, from about 0.68 to about 1.23 weight percent titanium dioxide, from about 0.67 to about 1.20 weight percent lead oxide, from about 0.26 to about 0.46 weight percent boron oxide, from about 0.82 to about 1.49 weight percent zinc oxide, and from 0 to about 0.11 weight percent manganese dioxide, wherein the capacitance of said composition varies with temperature about 15 percent or less from the capacitance at 25°C at temperatures between about -55°C and about 125°C.

12. A dielectric ceramic composition formed from (a) about 95.24 percent by weight of a base ceramic preparation consisting essentially of metal oxides or precursors thereof in proportions to provide, in the oxide form, about 98.31 weight percent barium titanate, about 1.40 weight percent niobium pentoxide, and 0.29 weight percent cobalt oxide; (b) about 4.76 percent by weight of a ceramic flux consisting essentially of metal oxides or precursors thereof in proportions to provide, in the oxide form, about 27.99 weight percent bismuth titanate (Bi2Ti2O7), about 40.02 weight percent lead titanate, about 24.4 weight percent zinc oxide and 7.6 weight percent boron oxide; and (c) manganese dioxide or precursors thereof in proportions to provide manganese dioxide in an amount of about 0.05 percent of the combined of the combined weight of said base ceramic preparation and said ceramic flux.

13. A method of making a dielectric ceramic composition which comprises:
(1) mixing (a) a base ceramic preparation consisting essentially of metal oxide or precursors thereof in proportions to provide, in the oxide form, from about 98.0 to about 99 weight percent barium titanate, from about 0.97 to about 1.54 weight percent niobium pentoxide, and from about 0.19 to about 0.32 weight percent cobalt oxide;
(b) a ceramic flux consisting essentially of metal oxides or precursors thereof in proportions to provide, in the oxide form, from about 16 to about 60 weight percent bismuth titanate (Bi2Ti2O7), about 8 to about 52 weight percent lead titanate, about 18 to about 35 weight percent zinc oxide, and about 5 to about 11 weight percent boron oxide; and (c) manganese dioxide or precursors thereof in proportions to provide manganese dioxide in an amount of from about 0 to about 0.114 percent of the combined weight of said base ceramic preparation and said ceramic flux.
(2) firing the resulting mixture at a temperature between about 1100°C and about 1140°C.

14. A method in accordance with Claim 13 wherein said mixture of said base ceramic preparation and said ceramic flux consists essentially of from about 3.5 to about 6.5 weight percent of said ceramic flux and of from about 96.5 to about 93.5 weight percent of said base ceramic preparation.

15. A method in accordance with Claim 13 wherein said mixture of said base ceramic preparation and said ceramic flux consists essentially of about 95 weight percent of said base ceramic preparation and 5 weight percent of said ceramic flux.